The overall objective of this project is to develop computational models for investigating flow induced platelet dynamics around and downstream of Mechanical Prosthetic Heart Valves (MPHVs). The underlying justification for the need for such a tool is the common understanding that current valve designs generate flows that are characterized by high shear stresses, turbulent fluctuations, and regions of blood recirculation, which in turn enhance the risk of thrombus formation by inducing platelet activation, and subsequent aggregation and deposition downstream of the valve. The aim is to develop a particulate-laden two-phase flow model of blood with two-way coupling, to incorporate the latter into an existing 3-D massively-parallel CFD software for grid-free simulation of unsteady laminar-turbulent incompressible flow, and to investigate the robustness of the developed technology using a set of benchmark tests. The specific aims of Phase I are (1) to implement and test a generic meshless two-phase flow solver with two-way coupling, and (2) to formulate specific models and boundary conditions that pertain to platelet dynamics, which can then be implemented and tested during Phase II.